#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int main()
{
    double num = 0;
    int i = 1;
    for (int a = 1; a <= 100; a++)
    {
        num += 1.0 / a * i;
        i = -i;
    }
    printf("%lf ", num);
    return 0;
}